Both high levels of polyamines and methylated bases have been shown to be affiliated with the onset of rapid cellular proliferation. S-Adenosyl-methionine (SAM) serves as the propylamino donor in the synthesis of polyamines and as the methyl donor in virtually all transmethylation reactions. The overall objective of this research proposal is to determine the SAM-related biochemical and genetic mechanisms associated with the initiation of mitosis. An excellent opportunity for studying the molecular events necessary for the initiation of mitosis is provided by the germination and outgrowth of yeast spores. Radioactive isotopes will be utilized to follow the relationship between polyamine biosynthesis and tRNA methylation to RNA, DNA, and protein synthesis during germination and outgrowth. The uptake and accumulation of putrescine, spermidine, and spermine will be monitored and the effect of extracellularly supplied polyamines on macromolecular biosynthesis will be ascertained. The levels of SAM decarboxylase, ornithine decarboxylase, SAM synthetase, 5'-methyl-thioadenosine nucleosidase and tRNA methylase will be monitored throughout the G1 interval of the mitotic cell cycle. The effect of inhibitors of transmethylation and/or polyamine biosynthesis on germination, outgrowth, and macromolecule synthesis will be explored to test the role of polyamines and the methylation of RNA as modulators of growth. In addition, we hope to isolate temperature-sensitive mutants which require putrescine, spermidine, and/or spermine for growth and, a temperature sensitive strain which lacks the RNA methylase activity. With these mutants we hope to rigorously control both polyamine biosynthesis and RNA methylation.